There is a growing demand for highly selective and efficient catalytic processes due to today's economical and environmental constraints in the chemical industries. Organometallic homogeneous catalysts seem ideally suited to answer this challenge since they offer higher activity and chemo-, regio-, and stereo-selectivity than their heterogeneous counterparts for a wide variety of reactions. In spite of these favorable properties, the number of homogeneous catalytic processes operating on an industrial scale is small. This has primarily been due to lack of efficient methods to recover expensive homogeneous catalysts from reaction mixtures and to recycle them.
Recovery and recycling of homogeneous catalysts is an active research area and a variety of methods are currently being investigated in many laboratories around the world. Among these, the use of aqueous biphasic catalysis is a very promising method and has been practiced on an industrial scale for production of n-butyraldehyde by hydroformylation of propylene. However, the low solubilities of most organic compounds in water may be prohibitive in extension of this technology to more hydrophobic reactants. Furthermore, a biphasic system is not preferable for reactions that are controlled by mass transfer.
There remains a need for homogeneous catalysis methods that provide ease of catalyst recovery and reuse, rapid mass transfer, and efficient conversion of reactants of various hydrophobicities.